Capsule endoscopy is booming and highly recognized in the international medical device field mainly because it has become an effective method for diagnosis of gastrointestinal diseases. A capsule endoscope comprises an imaging unit with solid state imaging element, a LED illumination unit, a wireless communication unit and other components all of which are incorporated in a capsule enclosure of a size suitable to be taken orally. After being swallowed by a subject, this capsule endoscope travels through the gastrointestinal (GI) tract of the subject while capturing images of the stomach or intestine and transmitting the images to an external data recorder through the wireless communication unit. The images can be displayed on a display screen. Based on the image information, the physician can make a diagnosis of gastrointestinal diseases for the subject in a painless and non-invasive state.
In order to make the capsule endoscope more flexible, controllable and more efficient, many foreign researchers have proposed to change the traditional capsule endoscope passively driven by digestive tract peristalsis to an actively-driven one. For example, PCT patent publication No. 01/35813 discloses a controllable capsule endoscope, which is controlled by driving the components of the capsule endoscope thereof. The capsule endoscope incorporates a reed switch. Said reed switch remains off under a certain intensity of magnetic field applied by an external magnetic device and is on when the intensity of the magnetic field is declined. Therefore, an effective navigation control of the capsule endoscope can be achieved by applying the magnetic field to the capsule endoscope to supply power to each constituent component. However, due to the use of the external magnetic device, any other magnetic components inside the capsule endoscope will have interference. Additionally, after the capsule endoscope is taken out of the package, it will take a certain period of time before being swallowed by the subject. During this wait period of time, the functions of the capsule endoscope remain active, so this is a problem because much power is wasted. For such a capsule endoscope with limited power supply, the waste of power may greatly affect the diagnosis. Besides, because of the influence of the magnetic field, it is difficult to solve the waste problem of the electrical power for the capsule endoscope with many magnetic components.
In order to use an external magnetic control system or any other magnetic components for positioning capability, a power control means other than a magnetic switch must be used. Thus, a RFID switch can become adopted. The wireless switch control method turns on the internal power supply of the capsule endoscope using an external start command. However, a big receiving antenna is required when RFID switch is used to control the power supply, which is difficult to achieve for a capsule endoscope with limited internal space.